Remark 2.21 (de Rham complexes) 
The fact that the bracket of a Lie algebroid satisfies the Jacobi identity, together with the morphism property
of the anchor, imply that the Lie algebroid exterior derivative \({\rm d}^{L}\)  satisfies \({\rm d}^{L}\circ {\rm d}^{L}=0\) .
Therefore, \((\Gamma (\Lambda ^{\bullet }),{\rm d}^{L})\)  is a cochain complex (see e.g. [1]}).
This will be particularly important in sections REF , REF .

